Three-dimensional in-situ stress modeling of tight conglomerate reservoirs: A case study of Triassic Baikouquan formation in the Mahu depression, Xinjiang Oilfield

Abstract

As a tight conglomerate reservoir, the Baikouquan formation reservoir in the Mahu depression is vital heterogeneous. The development model of unconventional oil and gas fields such as shale gas is copied in the early development process. Advanced horizontal wells and volumetric fracturing technologies are adopted, with high development costs and low economic benefits. During the development of tight conglomerate reservoirs, there are typical problems such as underdeveloped natural fractures, complex fracture formation mechanisms during fracturing, and serious interlayer channeling in fractured wells. Practical results show that the adequate characterization of in-situ stress distribution plays a decisive role in the scientific and efficient development of tight conglomerate reservoirs. To accurately characterize the three-dimensional in-situ stress distribution law of conglomerate reservoirs, the paper selects the Mahu 131 demonstration well area. The mechanical parameters of the demonstration area are finely described through a series of core tests, well-drilled logging data, and seismic inversion data. As a result, the spatial distribution of essential parameters of the demonstration area has been established, such as the three-dimensional elastic modulus attribute volume and the three-dimensional Poisson’s ratio attribute volume. Further, an advanced finite element simulator and large-scale parallel computing technology establish the test area’s high-precision three-dimensional stress field model. Based on enormous fracturing data, microseismic data, and production data, quality control and correction of the three-dimensional stress field model are carried out. The results show that the established geomechanical model accurately reflects the direction, magnitude, and heterogeneity of the in-situ stress in the demonstration area. Through the three-dimensional minimum in-situ stress distribution, the three-dimensional horizontal stress difference distribution, the lithology characteristics of conglomerate, rock mechanical properties, and other factors in the test area, it is believed that the difference in interlayer stress is the main reason for the interlayer channeling of fracturing. According to the established high-precision in-situ stress model and the rational fracturing construction process, it can actively strengthen or weaken the instantaneous and local stress field and pressure field, from near field to far-field, and promote the expansion of hydraulic fractures in the desired manner.